Transmission device, transmission method, and storage medium

ABSTRACT

Disclosed is a method that preferably performs transmission processing to a time sequence signal of a known pattern as the pre-amble and an OFDM transmitted signal. 
     In data communications, the general practice defines the pre-amble and detects the peaks of the mutual correlation to thereby detect synchronization. The pre-amble here is defined by the binary value in most cases for simplification of a correlation detecting device. In this case, the spectrum becomes irregular with sharp peaks and dips, which deteriorates the correlation characteristic. The method of the invention forcibly adjusts the spectrum amplitude of the pre-amble pattern on the transmitting side while retaining the phase information thereof, and thereby the method improves the spectrum and correlation characteristics while securing simplification of a correlation detecting device on the receiving side.

TECHNICAL FIELD

The present invention relates to a transmitting device, transmittingmethod, and storage medium that process radio transmitted signals. Theinvention specifically relates to a transmitting device, transmittingmethod, and storage medium that perform amplitude and phase modulationto carriers each, perform inverse FFT to the plural carriers to convertthem into time base signals while maintaining the orthogonality of thecarriers on the frequency axis, and perform transmission processing to atransmitted OFDM (Orthogonal Frequency Division Multiplexing) signal.

Further in detail, the invention relates to a transmitting device,transmitting method, and storage medium that perform transmissionprocessing to a known pattern signal for attaining synchronization onthe receiving side, specifically to a transmitting device, transmittingmethod, and storage medium that perform transmission processing to aknown pattern signal made up with a time sequence together with anOFDM-modulated transmitted signal.

BACKGROUND ART

The wireless LAN has attracted considerable attention as a system thatrelieves users from the troublesome wiring of the wired LAN. Thewireless LAN can eliminate most of wired cables in a workspace such asan office, which makes it possible to move personal computers and othercommunication terminals comparably easily. In recent years, accompaniedwith the enhanced speed and reduced price of the wireless LAN, thedemand for it is remarkably increased. Especially recently, the personalarea network (PAN) is under the examination for introduction, so thatpeople can communicate information with a small-scale wireless networkusing multiple electronic devices surrounding people. As an example,different wireless communication systems and wireless communicationdevices are stipulated, which use the frequency bandwidths that do notrequire a license by the supervising agency, such as 2.4 GHz band and 5GHz band.

Recently, a wireless communication system using an ultra wide bandwidthcovering 3 GHz to 10 GHz, which is called the ‘ultra wide band (UWB)communication’ has drawn considerable attention as a wirelesscommunication system that realizes a short-distance ultra-high speedtransmission; and the practical development thereof is expected. Atpresent, the data transmission system with a packet structure includingthe preamble is being designed as an access control system for the UWBcommunication in IEEE 820.15.3 and so forth.

Now, building up a wireless network in a room will make the multi-pathenvironments, in which the receiving devices receive a direct wavehaving multiple reflected waves and delayed waves overlapped. Themulti-path environments will cause delay distortion (or frequencyselective fading), which effects errors on the communication. And, theinter-symbol interferences due to the delay distortion will begenerated.

One of the main countermeasures for the delay distortion is themulti-carrier transmission system. Since the multi-carrier transmissionsystem distributes transmitted data to plural carriers of differentfrequencies, the bandwidths of the carriers each become narrow, whichmakes it difficult to receive the influences of the frequency selectivefading.

In the OFDM (Orthogonal Frequency Division Multiplexing) system beingone of the multi-carrier transmission systems, the frequencies of thecarriers each are set in a manner that the carriers each are mutuallyorthogonal in the symbol interval. During transmission of information,the system performs serial/parallel conversion to the informationtransmitted in serial at each symbol cycle that is slower than the datatransmission rate, allocates the plural data converted into theserial/parallel format to the carriers each, performs the amplitude andphase modulation to the carriers each, performs inverse FFT to theplural carriers, and thereby converts the carriers on the frequency axisinto the signals on the time base while retaining the orthogonality onthe frequency axis to transmit the information. During reception, thesystem performs the operation reverse to the above; that is, it performsFFT to convert the signals on the time base into the signals on thefrequency axis, performs the demodulations corresponding to therespective modulation systems to the carriers each, performsparallel/serial conversion to the demodulated signals, and reproducesthe original information transmitted in the serial format.

The OFDM modulation system is adopted as the standard for the wirelessLAN, for example, in IEEE 802.11a/g. Also in IEEE 802.15.3a, thestandardization of the UWB communication system adopting the OFDMmodulation system (hereunder, called ‘OFDM_UWB’) is in progress, inaddition to the DS-UWB system with the diffusion speed of DS informationsignal raised to the limit, and the impulse-UWB system for transmittingand receiving the information signal that uses the impulse signal stringhaving a very short cycle of about some 100 pico-seconds. In case of theOFDM_UWB communication system, the OFDM modulation is under examination,which performs frequency hopping (FH) on three sub-bands whosebandwidths are 528 MHz each in the frequency band covering 3.14 to 4.8GHz, and uses IFFT/FFT having each frequency band composed of 128 points(see Non-patent Document 1).

DISCLOSURE OF THE INVENTION

[Problem to be Solved by the Invention]

The general remote communication system with a transmitter and areceiver combined transmits the signal for attaining synchronization asa pre-amble (or middle-amble) in combination with a transmitted databody.

In case of the OFDM_UWB communication system as mentioned above, thetime sequence is used as the pre-amble signal for attainingsynchronization (see Non-patent Document 1). Further, the pre-amblesignal is configured with the pattern of the binary ±1, in order toreduce the computational complexity of the correlation processing on thereceiving side (because this case saves the multiplication forcalculating the correlation only through inverting the symbols).

FIG. 5 illustrates an example of the pre-amble signal of the binary ±1.In this case, the BPSK (Binary Phase Shift Keying) modulation isperformed to a known pattern made up with originally the time sequenceto generate the pre-amble signal, apart from the data body formed of theOFDM modulated signal for obtaining the time base signal by performingthe inverse FFT to the signal on the frequency axis. FIG. 6 typicallyillustrates a data frame configured with the pre-amble (orsynchronization-obtaining) signal having the BPSK modulation applied andthe data body having the OFDM modulation applied.

FIG. 7 illustrates the frequency spectrum of a binary time sequencesignal (pre-amble pattern) as shown in FIG. 5. As seen in the drawing,the binary time sequence signal forms a spectrum characteristic withsharp irregularities, which is not preferable for securing thestipulation for the transmission power density. Especially, the FCC(federal communications commission) rule concerning the UWB stipulatesthat the power density measured at each MHz must not exceed −41.3dBm/MHz, instead of the power of the total signals. Accordingly, in caseof the UWB system, the spectrum peaks are necessarily to be measured ata narrower interval than the sampling interval (for example, 4.125 MHz).In the example as shown in FIG. 7, the power spectrum at the peaks ofthe irregularities exceeds 0 dB (−41.3 dBm); therefore, to transmit thepre-amble as it is will face the situation that the power density cannotconform to the stipulation in the FCC rule. It is naturally necessary toconform to the FCC rule over the total data frame as shown in FIG. 5,not only with the OFDM modulated data body. In FIG. 7, since the peaks(near ±32 on the horizontal axis) exceed the limit by about 5 dB, it isnecessary to lower the transmission power of the pre-amble by 5 dB ontransmission. This will lead to deterioration of the S/N ratio.

FIG. 8 illustrates an auto-correlation characteristic of the pre-amblesignal. It is generally preferred that the output resides only near thecenter of the time base. In the drawing however, the output resides onthe peripheral areas of the time base (for example, near+16 on thehorizontal axis), and it is difficult to give a comment that thisauto-correlation characteristic is satisfactory.

In the OFDM modulation system, the general practice nullifies thesub-carriers on the center frequency band and both-end frequency bandsof the frequency domain in use (see FIG. 9). In this case, the spectrumof the pre-amble by the BPSK modulation as shown in FIG. 7 and thespectrum of the OFDM signal as shown in FIG. 9 are clearly different inthe waveforms; therefore, the receiving side has to switch the filterconditions in the pre-amble part and the OFDM signal part, which isinconvenient and disadvantageous.

[Non-Patent Document 1]

-   IEEE 802.15.3a TI Document<URL:-   http://grouper.ieee.org/groups/802/15/pub/2003/May03-   file name: 03142r2P802-15_TI-CFP-Document.doc>

An object of the invention is to provide an excellent transmittingdevice, transmitting method, and storage medium that can preferablyperform transmission processing to a known pattern signal such as apre-amble signal for obtaining synchronization on the receiving side.

Another object of the invention is to provide an excellent transmittingdevice, transmitting method, and storage medium that can preferablyperform transmission processing to a known pattern signal of the timesequence in combination with an OFDM modulated signal.

Another object of the invention is to provide an excellent transmittingdevice, transmitting method, and storage medium that can preferablyperform transmission processing, in a manner that both the time sequencesignal of a known pattern and the OFDM modulated signal satisfy thestipulation for the transmission power density without lowering the SNcharacteristic.

Another object of the invention is to provide an excellent transmittingdevice, transmitting method, and storage medium that can preferablyperform transmission processing to the time sequence signal of a knownpattern so as to improve the auto-correlation characteristic forobtaining synchronization and so forth.

[Means for Solving the Problem]

The invention has been made in view of the above problems, and relatesto a transmitting device that processes radio transmitted signals. Andit includes: a frequency conversion means that converts an original timesequence signal of a known multi-valued pattern into a frequency signalto attain a spectrum characteristic, a spectrum characteristicprocessing means that forcibly changes an amplitude of a spectrum signalwhile retaining the phase information of the spectrum, and a means thatreconverts a spectrum having the spectrum characteristic processingapplied into a time sequence signal.

The transmitting device relating to the invention transmits thereconverted time sequence signal as a pre-amble signal for obtainingsynchronization on the receiving side, together with a data body.

The transmitting device relating to the invention may further include amodulation processing means that modulates a transmitted data body toobtain a modulated signal for transmission. The modulation processingmeans performs amplitude and phase modulation to the carriers each bythe OFDM modulation system as an example, performs inverse FFT to theplural carriers, and thereby converts the original transmitted signal onthe frequency axis into a signal on the time base while retaining theorthogonality of the carriers each.

The spectrum characteristic processing means forcibly changes a spectrumamplitude of an original time sequence signal, in a manner that thespectrum amplitude of the original time sequence signal becomes equal tothat of a modulated signal for transmission, while retaining the phaseinformation of the spectrum of the original time sequence signal. As anexample, the spectrum characteristic processing means forcibly nullifiesthe spectrum amplitude on the center frequency band and both-endfrequency bands of the frequency domain in use, and smoothes thespectrum amplitude on the other regions, in a manner that the spectrumamplitude of the original time sequence signal becomes equal to that ofthe general OFDM signal while retaining the phase information of theoriginal time sequence signal.

Thus, according to the invention, it is possible to transform thepre-amble signal of the time sequence to be equivalent to the spectrumwaveform of the general OFDM signal. Accordingly, it is possible for thereceiving side to apply the same filter (low pass filter or band passfilter) to each of the signal frequency bands, which simplifies theconstruction on the receiving side.

The smoothing is applied to the spectrum except the DC components andthe components at the both-end frequency bands of the pre-amble signal.Thereby, in a new spectrum with the waveform shaping applied, the peaksof the irregularities are suppressed. This makes it easy to meet thestipulation for the transmission power density by the FCC and so forth,and makes it possible to attain a higher transmission power forobtaining the same SN characteristic.

The correlation processing on the time base is performed by theconvolution operation, which however corresponds to the product ofconjugate complex numbers on the frequency axis. Therefore, in thecorrelation calculation on the center frequency, only the real partremains as the result of the multiplication of the conjugate complexnumbers, and it is possible to obtain a greater value by retaining thephase information. Therefore, the above operation of processing thespectrum amplitude while retaining the phase information of the originaltime sequence signal will lead to eliminating the irregularities on thespectrum of the pre-amble signal, securing the stipulation for the powerdensity, and permitting the maximum transmission power.

[Effect of the Invention]

According to the invention, it is possible to provide an excellenttransmitting device, transmitting method, and storage medium that canpreferably perform transmission processing, in a manner that both thetime sequence signal of a known pattern as the pre-amble and the OFDMmodulated signal satisfy the stipulation for the transmission powerdensity without lowering the SN characteristic.

According to the invention, it is possible to provide an excellenttransmitting device, transmitting method, and storage medium that canpreferably perform transmission processing to the time sequence signalof a known pattern as the pre-amble so as to better the auto-correlationcharacteristic for obtaining synchronization and so forth.

According to the invention, it is possible to provide an excellenttransmitting device, transmitting method, and storage medium that canpreferably perform transmission processing to the time sequence signalof a known pattern by shaping the spectrum waveform arbitrarily, so asnot to increase the scale of a device for detecting the correlation onthe receiving side.

According to the invention, the spectrum amplitude of the pre-amblepattern on the transmitting side is forcibly adjusted while the phaseinformation thereof is retained, which makes it possible to improve thespectrum and correlation characteristics while securing simplificationof a correlation detecting device on the receiving side.

Other objects and features of the invention will become apparent by moredetailed descriptions based on the embodiments described later andaccompanying drawings.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the invention will be described in detail withreference to the accompanying drawings.

FIG. 1 typically illustrates a construction of the wirelesscommunication system relating to one embodiment of the presentinvention. As shown in the drawing, the wireless communication systemincludes a transmitter that transmits a radio signal and a receiver thatreceives the radio signal.

The wireless communication system relating to this embodiment adopts theUWB system that performs the wireless communication using the ultrawideband covering 3 GHz to 10 GHz in order to realize a short-distanceand ultra high-speed transmission. In view of the problem of the delaydistortion and inter-symbol interference under the multi-pathenvironments, it also adopts the OFDM modulation system that transmitsto convert plural sub-carriers arranged on the frequency axis into thesignal on the time base. The gist of the invention is to transmit thepre-amble signal of the time sequence, in consideration for thestipulation for the transmission power density, the auto-correlationcharacteristic, and the waveform of the spectrum; and the transmissionsystem of the data body is not specifically restricted.

The transmitter 10 includes a pre-amble generation unit 11 thatgenerates a pre-amble signal composed of a known pattern for attainingsynchronization, an OFDM modulation unit 12 that performs the OFDMmodulation to transmitted data, an RF unit 13 that up-converts the dataframe composed of the pre-amble and the data body into a radio signal,and an antenna 14 that transmits the radio signal to propagation paths.FIG. 10 illustrates an internal construction of the pre-amble generationunit 11. As shown in the drawing, the pre-amble generation unit 11includes a time-frequency conversion unit 11A, a spectrum characteristicprocessing unit 11B, and a frequency-time conversion unit 11C.

In this embodiment, the pre-amble signal for attaining synchronizationis made up with the time sequence of a multi-valued pattern in order toreduce the computational complexity of the correlation processing on theside of the receiver 20. The method of configuring the pre-amble signalwill be described later.

On the other hand, the receiver 20 includes an antenna 21 that receivesthe radio signal on the propagation paths, an RF unit 22 thatdown-converts a received signal, a synchronization processing unit 23that attains synchronization by the correlation processing between thereceived pre-amble signal and the known pattern retained in advance, andan OFDM demodulation unit 24 that performs the OFDM demodulation to thereceived data body to restore the original frequency signal.

The wireless communication system relating to this embodiment adopts theOFDM_UWB system, and employs a binary time sequence signal as thepre-amble signal for attaining synchronization, in order to simplify thecorrelation detecting device on the receiving side (see Non-patentDocument 1). However, the spectrum of this pre-amble signal formsirregularities with sharp peaks and dips, which deteriorates thecorrelation characteristic.

Accordingly, the wireless communication system in this embodimentforcibly adjusts the spectrum amplitude of the pre-amble pattern whileretaining the phase thereof on the transmitting side, and therebyimproves the spectrum and the correlation characteristic whilesimplifying the correlation detecting device on the receiving side.

The pre-amble generation unit 11 is provided with an original timesequence signal composed of a known multi-valued pattern as thepre-amble signal. This original pre-amble signal is made up with thebinary value of ±1, which is provided by the BPSK modulation, forexample, or as the data stored in a ROM (not illustrated). Here, thepre-amble signal is binary (case of BPSK modulation), however it maytake a multi-value, for example, +1, 0, −1 more than the binary value.

The time-frequency conversion unit 11A performs the frequency conversionby the Fourier transform to the original pre-amble signal h_(k) of thistime sequence signal to produce a spectrum characteristic H_(k). And,the spectrum characteristic processing unit 11B converts this H_(k) intoa new spectrum characteristic G_(k).

As the first procedure for converting the spectrum characteristic H_(k)into G_(k), the spectrum characteristic processing unit 11B performs awaveform shaping in a manner that the spectrum waveform of the pre-amblesignal part matches with that of the other OFDM signal part. Concretely,the spectrum characteristic processing unit 11B forcibly nullifies thespectrum amplitude, the DC components on the center frequency band andthe components on the both-end frequency bands of the frequency domainin use, and smoothes the spectrum amplitude on the other frequency bandsin a manner that the spectrum of the pre-amble signal becomes equal tothat of the general OFDM signal.

FIG. 2 illustrates a state that the spectrum characteristic processingunit 11B forcibly nullifies the DC components and the components on boththe ends of the original spectrum H_(k), and smoothes the spectrum onthe other frequency regions. As the result of shaping the spectrumwaveform, the spectrum of the pre-amble signal becomes equal to thespectrum amplitude of the OFDM_UWB part, which facilitates handling.Concretely, by nullifying the DC components (center frequency part) andthe components on both the ends of the frequency domain in use, thespectrum of the pre-amble signal becomes equal to the spectrum amplitudeof the general OFDM signal, which makes it possible for the receivingside to apply the same filter (low pass filter or band pass filter) tothe signal components each, thereby simplifying the configuration of thereceiver.

Applying the smoothing to the spectrum except the DC components and thecomponents on both the ends will suppress the peaks of theirregularities in a new spectrum G_(k). This makes it easy to meet thestipulation for the transmission power density by the FCC and so forth,and makes it possible to attain a higher transmission power forobtaining the same SN characteristic.

The smoothing of the spectrum is achieved by the following formula. Thatis, by using the following formula, the original time sequence signal ofthe binary pattern produces a normalized pre-amble signal so as to makethe spectrum flat.

$\begin{matrix}{G_{k} = \frac{H_{k}}{H_{k}}} & \left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\end{matrix}$

As the second procedure for converting the spectrum characteristic H_(k)into G_(k), the spectrum characteristic processing unit 11B forciblynullifies the spectrum amplitude while retaining the phase informationof the spectrum.

Here, the correlation processing on the time base is performed by theconvolution operation, which however corresponds to the product ofconjugate complex numbers on the frequency axis. The operations of thecorrelation processing on the time base and the frequency axis are givenby the following formulae.s(τ)=∫_(−∞) ^(∞) g(t)h*(t+τ)dtS(f)=G(f)H*(f)  [Formula 2]

The object of the correlation processing is h*(t+τ) in the aboveformula. The correlation calculation on the center frequency correspondsto the case of τ=0 on the time base in the above formula. On thefrequency axis, only the real part remains as the result of themultiplication of the conjugate complex numbers, and it is possible toobtain a greater value.

Therefore, the above operation of processing the spectrum amplitudewhile retaining the phase information eliminates the irregularities onthe spectrum of the pre-amble signal, secures the stipulation for thepower density, and permits the maximum transmission power.

The frequency-time conversion unit 11C performs the inverse FFT to thespectrum G_(k) thus obtained to restore a time sequence signal g_(k).The obtained time sequence signal can be used as the pre-amble signal onthe transmitting side.

FIG. 3 illustrates an example of the pre-amble signal g_(k) that isobtained from the original time sequence signal of the binary patternthrough the above processing. FIG. 4 illustrates an example of themutual correlation processing between the transmitted pre-amble signaland the received pre-amble signal. The pre-amble signal g_(k) is not ofthe binary pattern. However, as seen in the drawing, the correlation isenhanced remarkably on the center of the time base, and the correlationon the peripheral time domain is suppressed to a low level, whichconfirms that the correlation characteristic is enhanced.

FIG. 12 through FIG. 16 illustrate concrete examples of the pre-amblesignal sequences attained by using the original time sequence signals ofthe binary pattern through the spectrum smoothing processing relating tothe invention. The pre-amble signal sequences in FIG. 12 through FIG. 16each have different original time sequence signals as the elements.Here, the Sequence Element represents the number of the time sample, andthe Value represents the amplitude of each sample. With regard to theFormula 1, the tables in FIG. 12 through FIG. 16 give the results inwhich the inverse Fourier transform is performed to the signal G_(k)with the spectrum waveform shaped on the frequency domain.

The transmitter 10 stores the original time sequence signals of thebinary value of ±1, for example, as the law data of the pre-amble signalin a ROM, for example. And the following processing may be made: readingan original time sequence signal each time of data transmission;according to the above procedure, performing the Fourier Transform toapply the processing to the spectrum amplitude while retaining the phaseinformation, and thereafter, performing the inverse Fourier Transform tosequentially generate the pre-amble signal.

If the original time sequence signals as the law data of the pre-amblesignal are the same, it will always give one and the same pre-amblesignal; accordingly, the sequential pattern once calculated on thetransmitter 10 may be stored in the ROM as the pre-amble signal fortransmission.

FIG. 11 illustrates a construction of the transmitter 10 in this case.The transmitter 10 in FIG. 11 stores the once-calculated sequentialpattern in a pre-amble signal storage unit 11′ as the pre-amble signalfor transmission, which is different form the transmitter 10 as shown inFIG. 1, where the pre-amble generation unit 11 sequentially generatesthe normalized pre-amble signal to make the spectrum flat.

The pre-amble signal g_(k) in this case deviates from the binarypattern. However, the transmitter side can store the pre-amble patternin a ROM or the like as the transmitted data itself, and can use it.Therefore, the deviation from the binary pattern will not cause anyproblem. And the receiver side may use the binary as it is, inconsideration for easily making up the device.

Instead of calculating the pre-amble signal for transmission on thetransmitter 10 on the basis of the known original time sequence signalprovided in advance, it is also acceptable for a manufacturer of thedevice to calculate the pre-amble signal from the known original timesequence signal by using the above procedure, and to mount on thetransmitter 10 the ROM in which not the original time sequence signalbut the actual pre-amble pattern is stored.

The invention has thus been described in detail with reference tospecific embodiments. However, it is apparent that a person havingordinary skill in the art is able to make modifications and changes tothe aforementioned embodiments without a departure from the gist of theinvention. That is, the embodiments have been presented as illustrationsfor disclosing the invention, and the contents described here in thisspecification should not be understood in a restricted manner. Thecontents of the claims should be well considered for understanding thespirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1]

FIG. 1 typically illustrates a construction of the wirelesscommunication system relating to one embodiment of the presentinvention.

[FIG. 2]

FIG. 2 illustrates a state in which the DC components of the originalspectrum H_(k) and the components on both the ends thereof are forciblynullified, and the amplitudes of the spectrum on the other regions aresmoothed.

[FIG. 3]

FIG. 3 illustrates an example of the pre-amble signal obtained from theoriginal time sequence signal of the binary pattern.

[FIG. 4]

FIG. 4 illustrates an example of the mutual correlation processingbetween the transmitted pre-amble and the received pre-amble.

[FIG. 5]

FIG. 5 illustrates an example of the pre-amble signal of the value ±1.

[FIG. 6]

FIG. 6 typically illustrates a data frame configured with the pre-amble(or synchronization-obtaining) signal with the BPSK modulation appliedand the data body with the OFDM modulation applied.

[FIG. 7]

FIG. 7 illustrates the frequency spectrum of a time sequence signal asshown in FIG. 5.

[FIG. 8]

FIG. 8 illustrates an auto-correlation characteristic of the pre-amblesignal.

[FIG. 9]

FIG. 9 illustrates a construction of the OFDM signal, in which thesub-carriers on the center and both the ends of the frequency domain inuse are nullified.

[FIG. 10]

FIG. 10 illustrates an internal construction of the pre-amble generationunit 11.

[FIG. 11]

FIG. 11 illustrates another construction of the transmitter 10.

[FIG. 12]

FIG. 12 illustrates a concrete example of the pre-amble signal sequenceattained by using the original time sequence signal of the binarypattern through the spectrum smoothing processing relating to theinvention.

[FIG. 13]

FIG. 13 illustrates a concrete example of the pre-amble signal sequenceattained by using the original time sequence signal of the binarypattern through the spectrum smoothing processing relating to theinvention.

[FIG. 14]

FIG. 14 illustrates a concrete example of the pre-amble signal sequenceattained by using the original time sequence signal of the binarypattern through the spectrum smoothing processing relating to theinvention.

[FIG. 15]

FIG. 15 illustrates a concrete example of the pre-amble signal sequenceattained by using the original time sequence signal of the binarypattern through the spectrum smoothing processing relating to theinvention.

[FIG. 16]

FIG. 16 illustrates a concrete example of the pre-amble signal sequenceattained by using the original time sequence signal of the binarypattern through the spectrum smoothing processing relating to theinvention.

Explanation of Reference Numerals

-   10 . . . transmitter-   11 . . . pre-amble generation unit-   11′ . . . pre-amble signal storage unit-   12 . . . OFDM modulation unit-   13 . . . RF unit-   14 . . . antenna-   20 . . . receiver-   21 . . . antenna-   22 . . . RF unit-   23 . . . synchronization processing unit-   24 . . . OFDM demodulation unit

The invention claimed is:
 1. A transmitting device that processes radiotransmitted signals, comprising: a frequency conversion means forconverting an original time sequence signal of a known multi-valuedpattern into a frequency signal to attain a spectrum characteristic; aspectrum characteristic processing means for changing an amplitude ofthe frequency signal while retaining phase information of the frequencysignal; means for reconverting the frequency signal having the spectrumcharacteristic processing applied into a time sequence signal; means fortransmitting a signal reconverted into the time sequence signal as apre-amble signal for attaining synchronization at a receiver togetherwith a data body; and modulation processing means for modulating thedata body to attain a modulated signal for transmission, wherein themodulated signal is transmitted together with the pre-amble signal,wherein the modulation processing means performs an OFDM modulation thatapplies amplitude and phase modulation to each of a plurality ofcarriers, applies inverse FFT to the plurality of carriers, and convertsthe carriers into signals on the time base, while retainingorthogonality of each of the plurality of carriers on the frequencyaxis, and the spectrum characteristic processing means sets a spectrumamplitude of an original time sequence signal to a specific value at acenter frequency band and end frequency bands of a frequency domain inuse, and smoothes the spectrum amplitude at the other frequency bands,in a manner that the spectrum amplitude of the original time sequencesignal becomes equal to that of a general OFDM signal while retainingphase information of the original time sequence signal.
 2. Atransmitting device according to claim 1, wherein the spectrumcharacteristic processing means nullifies the spectrum amplitude on thecenter frequency band and end frequency bands.
 3. A transmitting methodperformed at a transmitting device that processes radio transmittedsignals, comprising: converting an original time sequence signal of aknown multi-valued pattern into a frequency signal to attain a spectrumcharacteristic; changing an amplitude of the frequency signal whileretaining phase information of the frequency signal; reconverting thefrequency signal having the spectrum characteristic processing appliedinto a time sequence signal; transmitting a signal reconverted into thetime sequence signal as a pre-amble signal for attaining synchronizationat a receiver together with the data body; and modulating, at amodulator, the data body to attain a modulated signal for transmission,wherein the modulated signal is transmitted together with the pre-amblesignal, wherein the modulating includes performing an OFDM modulationthat applies amplitude and phase modulation to each of a plurality ofcarriers, applying inverse FFT to the plurality of carriers, andconverting the plurality of carriers into signals on the time base,while retaining the orthogonality of each of the carriers on thefrequency axis, and the changing includes setting a spectrum amplitudeof an original time sequence signal to a specific value at a centerfrequency band and end frequency bands of a frequency domain in use, andsmoothing the spectrum amplitude at the other frequency bands, in amanner that the spectrum amplitude of the original time sequence signalbecomes equal to that of a general OFDM signal while retaining phaseinformation of the original time sequence signal.
 4. A transmittingmethod according to claim 3, wherein the changing includes nullifyingthe spectrum amplitude on the center frequency band and end frequencybands.
 5. A transmitting device that processes radio transmittedsignals, comprising: a frequency conversion means for converting anoriginal time sequence signal of a known multi-valued pattern into afrequency signal to attain a spectrum characteristic; a spectrumcharacteristic processing means for changing an amplitude of thefrequency signal while retaining phase information of the frequencysignal; means for reconverting the frequency signal having the spectrumcharacteristic processing applied into a time sequence signal; and apre-amble pattern storage means for storing the signal reconverted intothe time sequence signal as a pre-amble signal for attainingsynchronization at a receiver, wherein the pre-amble signal read fromthe pre-amble pattern storage means is transmitted together with atransmitted data body, wherein the spectrum characteristic processingmeans sets a spectrum amplitude of the original time sequence signal toa specific value at a center frequency band and end frequency bands of afrequency domain in use, and smoothes the spectrum amplitude at theother frequency bands, in a manner that the spectrum amplitude of theoriginal time sequence signal becomes equal to that of a general OFDMsignal while retaining phase information of the original time sequencesignal.
 6. A transmitting method performed at a transmitting device thatprocesses radio transmitted signals, comprising: converting an originaltime sequence signal of a known multi-valued pattern into a frequencysignal to attain a spectrum characteristic; changing an amplitude of thefrequency signal while retaining phase information of the frequencysignal; reconverting the frequency signal having the spectrumcharacteristic processing applied into a time sequence signal; andstoring, at a memory, the signal reconverted into the time sequencesignal as a pre-amble signal for attaining synchronization at areceiver, wherein the pre-amble pattern stored in advance is read outand transmitted together with a transmitted data body, wherein thechanging includes setting a spectrum amplitude of the original timesequence signal to a specific value at a center frequency band and endfrequency bands of a frequency domain in use, and smoothing the spectrumamplitude at the other frequency bands, in a manner that the spectrumamplitude of the original time sequence signal becomes equal to that ofa general OFDM signal while retaining phase information of the originaltime sequence signal.
 7. A transmitting device that processes radiotransmitted signals, comprising: a time-frequency conversion unitconfigured to convert an original time sequence signal of a knownmulti-valued pattern into a frequency signal to attain a spectrumcharacteristic; a spectrum characteristic processing unit configured tochange an amplitude of the frequency signal while retaining phaseinformation of the frequency signal; a frequency-time conversion unitconfigured to convert the frequency signal having the spectrumcharacteristic processing applied into a time sequence signal; aradio-frequency unit configured to transmit a signal reconverted intothe time sequence signal as a pre-amble signal for attainingsynchronization at a receiver together with a data body; and amodulation unit configured to modulate the data body to attain amodulated signal for transmission, wherein the modulated signal istransmitted together with the pre-amble signal, wherein the modulationunit is configured to perform an OFDM modulation that applies amplitudeand phase modulation to each of a plurality of carriers, applies inverseFFT to the plurality of carriers, and converts the carriers into signalson the time base, while retaining orthogonality of each of the pluralityof carriers on the frequency axis, and the spectrum characteristicprocessing unit is configured to set a spectrum amplitude of an originaltime sequence signal to a specific value at a center frequency band andend frequency bands of a frequency domain in use, and smoothes thespectrum amplitude at the other frequency bands, in a manner that thespectrum amplitude of the original time sequence signal becomes equal tothat of a general OFDM signal while retaining phase information of theoriginal time sequence signal.
 8. A transmitting device that processesradio transmitted signals, comprising: a time-frequency conversion unitconfigured to convert an original time sequence signal of a knownmulti-valued pattern into a frequency signal to attain a spectrumcharacteristic; a spectrum characteristic processing unit configured tochange an amplitude of the frequency signal while retaining phaseinformation of the frequency signal; a frequency-time conversion unitconfigured to reconvert the frequency signal having the spectrumcharacteristic processing applied into a time sequence signal; and amemory configured to store the signal reconverted into the time sequencesignal as a pre-amble signal for attaining synchronization at areceiver, wherein the pre-amble signal read from the memory istransmitted together with a transmitted data body, wherein the spectrumcharacteristic processing unit is configured to set a spectrum amplitudeof the original time sequence signal to a specific value at a centerfrequency band and end frequency bands of a frequency domain in use, andsmoothes the spectrum amplitude at the other frequency bands, in amanner that the spectrum amplitude of the original time sequence signalbecomes equal to that of a general OFDM signal while retaining phaseinformation of the original time sequence signal.